Thin-film photovoltaic modules, a variety of which is also known as thin-film solar modules, are generally composed of a number of electrically interconnected optoelectronic components. Such components may be optoelectronic devices such as photovoltaic cells and additional optional components such as diodes and other electronic devices. Photovoltaic modules usually also include electrically interconnecting components such as cell-to-cell connectors and busbars.
Multilayer thin-film technologies enable the monolithic integration and interconnection of several optoelectronic components and associated components on a same substrate. This integration is produced in situ using a sequence of layer deposition and scribing techniques. Thin-film optoelectronic or photovoltaic components or devices are essentially composed of a stack of three material layers: a conducting back-contact electrode layer, a semiconductive photovoltaic material layer, also known as the absorber, and another conducting front-contact electrode layer, said front-contact layer usually being transparent. Photovoltaic cells based on semiconductive material such as Cu(In,Ga)Se2 (CIGS) or CdTe show a high potential for less expensive solar electricity, lower energy payback time, and improved life-cycle impact as compared to traditional wafer-based silicon photovoltaic devices or solar cells.
Compared to wafer-based photovoltaic devices, monolithic photovoltaic modules may have lower costs thanks to reduced material quantities used by thin films, reduced labor costs of monolithic integration, and ease of automatic production of large quantities of photovoltaic modules, for example using roll-to-roll manufacturing techniques. Further savings can be obtained by increasing the relative area of photovoltaic components exposed to light, for example by reducing the area occupied by: front-contact grids that collect current over the photovoltaic cell's front-contact electrode, electrical interconnects between optoelectronic components, and busbars. Photovoltaic module production yields may also be increased thanks to a reduction in the number of production steps, for example by reducing the number of scribing operations needed to delineate and structure the interconnects of optoelectronic components in thin-film monolithic photovoltaic modules.
Photovoltaic modules have been developed that attempt to reduce losses induced by electrical component shadowing over photovoltaic components or areal occupancy over the light exposed side. For example U.S. Pat. No. 7,649,141 describes a thin silicon wafer with laser-drilled wrap-through conducting holes, also known as vias, that connect the front-contact components to back-contact components, thereby avoiding shadowing by grid components laid on the front-contact surface, with the benefit of high current collection efficiency. U.S. Pat. No. 7,276,724 describes series-interconnected optoelectronic device modules thanks to the forming of vias, for example using laser ablation, and the addition of conductive material to drive current between front and backside top electrodes as well as to a second adjacent module. U.S. Pat. No. 7,276,724 uses laser drilling to create circular isolation trenches and notices that this may cause short circuits between front- and back-contacts that are undesirable on the outer circumference of the trench but desirable on the inner circumference. U.S. Pat. No. 7,276,724 describes designs for the series interconnection of optoelectronic device modules, each including a device layer on a 100 microns-thick back-contact electrode, itself separated by an insulating layer from a backside top electrode, said optoelectronic device modules being attached to an insulating carrier substrate.
Although wrap-through vias are highly advantageous to reduce shading and increase relative exposed surface, a problem with their manufacture is that they usually require drilling and subsequent metallizing. This requires additional production steps which may add costs and decrease yield. Some of these steps can be avoided with the monolithic optoelectronic module production method described in the present invention.